From Os Guinness, Fools Talk:

First the problem caused by sin:

“Were Adam and Eve aware of what they were doing? The thrust of the biblical account of the fall is powerful. Their disobedience entailed two things that are now characteristic of all of us as humans. On the one hand, for each of us, sin is the claim to the right to myself, and so to my way of seeing things, which—far more than class, gender, race and generation—is the ultimate source of human relativity. On the other hand, sin is the deliberate repudiation of God and the truth of his way of seeing things. If my way of seeing things is decisive, anyone who differs from me is wrong by definition—including God. No, especially God, because his way of seeing things is more powerful and therefore more threatening than anyone else’s. His word, our interference. This last point means, in turn, that sin, and the mistrust of disbelief in which it issues, does not, will not and cannot see God as he truly is. Still knowing God, it must now always refuse to face the responsibility of its knowledge of God and of its own guilt. It must therefore pass the buck. So when God asks Adam what he has done, he ducks the question by blaming Eve, just as Eve in her turn deflects the question by blaming the serpent.”

This brings us to the purpose of apologetics:

“Here at this precise point lies the core reason for Christian advocacy, as well as its motivating passion. Apologetics (from apologia in Greek) is a “word back,” a reasoned defense mounted on behalf of the one we love who is innocent but has been falsely and unfairly accused. Faith desires to let God be God. Sin has framed God, whether by the ultimate insults that he, the creator of all things, does not exist, or that he, the white-hot holy One, is responsible for the evil and suffering that humans have introduced into his good creation. So God’s name must be cleared and his existence and character brought to the fore beyond question.”